1. Field of the Invention
Embodiments of the present invention generally relate to substrate processing systems. More specifically, the invention relates to a physical vapor deposition chamber of a substrate processing system.
2. Description of the Related Art
Physical vapor deposition (PVD), or sputtering, is one of the most commonly used processes in fabrication of electronic devices. PVD is a plasma process performed in a vacuum chamber where a negatively biased target is exposed to a plasma of an inert gas having relatively heavy atoms (e.g., argon (Ar)) or a gas mixture comprising such inert gas. Bombardment of the target by ions of the inert gas results in ejection of atoms of the target material. The ejected atoms accumulate as a deposited film on a substrate placed on a substrate pedestal disposed within the chamber.
A ground shield may be disposed in the chamber to help define a processing region in a desired region within the chamber with respect to the substrate. The ground shield helps confine the plasma within the processing region. Confining the plasma and the ejected atoms to the processing region helps maintain other components in the chamber free from deposited materials and promotes more efficient use of target materials, as a higher percentage of the ejected atoms are deposited on the substrate.
The ground shield is electrically coupled to the vacuum chamber walls and is electrically isolated from the target. As such, the ground shield is typically attached to the walls, or body, of the vacuum chamber. In addition, a small gap is maintained between the edge of the ground shield and the target to prevent the plasma from forming outside of the processing region. However, it is difficult to align the ground shield and the target to maintain the small gap therebetween, resulting in time consuming set-up and maintenance costs for proper operation of the apparatus. This effect is exacerbated by the use of larger targets, required for processing larger substrates. For example, substrates for use in the manufacture of flat panel displays have grown to about 15,000 cm2 and above. In addition, even larger substrates are envisioned in the future.
Therefore, there is a need in the art for an improved ground shield for use in a PVD chamber.